1. Field of the Invention
The present invention relates to a track frame structure of a crawler-type construction machine.
2. Description of Prior Art
As shown in FIGS. 7 and 8, as a traveling apparatus of a crawler-type construction machine such as a bulldozer, a hydraulic excavator and the like, there is a hydraulically driven type crawler traveling apparatus in which a mounting frame assembly (constituted by a bracket or the like) 3B of a crawler drive reduction gear 11 with a hydraulic motor is integrally connected to a rear end side of a track frame 1B for a crawler via a joint plate 2B, the crawler drive reduction gear 11 with the hydraulic motor is mounted, and a sprocket 15 mounted to a crawler drive wheel 8 provided in the crawler drive reduction gear 11 is engaged with a crawler 14, thereby rotating the crawler 14 due to a hydraulic drive force so as to travel.
Since the hydraulically driven type crawler traveling apparatus mentioned above is provided with the joint plate 2B integrally connecting the mounting frame assembly 3B of the crawler drive reduction gear 11 with the hydraulic motor, in the rear end side of the crawler track frame 1B, it is impossible to move a mounting position of a track roller 6r mounted to a rearrest end side of the track frame 1B close to a side of the crawler drive wheel 8, so that there is a problem that a crawler actual ground contact length between the track roller 6r and a track roller 6f mounted to a frontmost end side of the track frame 1B is shorter than a normal mechanical drive type crawler traveling apparatus.
The actual ground contact length means a length L0 in which the crawler 14 is actually in contact with the ground between the track roller 6f at the frontmost end of the track frame 1B and the track roller 6r at the rearmost end of the track frame 1B, as shown in FIG. 7, however, when the actual ground contact length L0 is short, a stability in a longitudinal direction of a vehicle body is reduced, and an angle of incline in the longitudinal direction of the vehicle body is increased at a time when the crawler 14 runs on a protruding object, whereby a fluctuation of height of a working implement such as a blade or the like from the ground is increased, so that there is generated a problem that a ground leveling operability is not good.
As an improvement against the problem mentioned above, there is a structure disclosed in Japanese Patent Application Laid-open No. 9(1997)-142343, however, it can not provide a track frame structure capable of making the crawler actual ground contact length longer.
The present invention is made for the purpose of solving the problem mentioned above, and an object of the present invention is to provide a track frame structure in which a track roller at a rearmost end side of the track frame can be mounted without being interfered with a joint plate so as to increase a crawler actual ground contact length.
In order to achieve the object mentioned above, in accordance with a first aspect of the present invention, there is provided a track frame structure in which a mounting frame assembly of a crawler drive reduction gear with a hydraulic motor is mounted to an end portion of a track frame 1 of a crawler-type construction machine via a joint plate 2,
wherein a notch portion, notched so as to have a size to which a roller portion of a track roller is inserted, is provided in a lower side plate portion of the joint plate, and a roller portion of a track roller mounted to a rearmost end side of the track frame is inserted and mounted within the notch portion, whereby the track roller in the rearmost end side of the track frame can be arranged close to a crawler drive wheel side.
In accordance with the first aspect of the present invention, since the structure is made such that the roller portion of the track roller mounted to the rearmost end side of the track frame can be inserted and mounted within the notch portion formed in the joint plate, it is possible to move the track roller in the rearmost end side of the track frame close to the crawler drive wheel side.
Accordingly, it is possible to increase the crawler actual ground contact length and it is possible to improve stability and a ground leveling operability at a time when the vehicle travels and works.
In accordance with a second aspect of the present invention, there is provided a track frame structure as recited in the first aspect, wherein the lower side plate portion having the notch portion notched so as to have the size to which the roller portion of the track roller is inserted in the joint plate is constituted by a joint plate formed by bending to a side of the crawler drive wheel, the roller portion of the track roller mounted to the rearmost end side of the track frame is inserted within the notch portion, and a rotary shaft receiving portion of the track roller is mounted close to a bent side of the joint plate, whereby the track roller in the rearmost end side of the track frame can be arranged close to the crawler drive wheel side.
In accordance with the second aspect of the present invention, it is possible to increase a length of the rear end side in a lower surface of the track frame toward a rearward portion by bending the lower side of the joint plate, and it is possible to move a mounting position of a track roller bearing mounted to the lower surface in the rearmost end side of the track frame further close to the crawler drive wheel side.
Further, the notch portion to which the roller portion of the track roller is inserted is formed in the plate bent portion, whereby it is possible to move the track roller in the rearmost end side of the track frame further close to the crawler drive wheel side so as to make the crawler actual ground contact length longer in comparison with the first aspect, and it is possible to further improve the traveling stability and the ground leveling operability of the vehicle.